In recent years, the wavelength division multiplexing (WDM) technology has been used in the field of an optical network, where the WDM technology allows a large capacity optical transmission to be achieved by performing wavelength division multiplexing for different wavelengths to transmit large-capacity data. According to the WDM technology, an optical add drop multiplexer (OADM) configured to add an optical signal with an arbitrary wavelength to a group of WDM signals and drop an optical signal with an arbitrary wavelength from the WDM signal group for reception is often used.
When an optical signal with another wavelength is added to the WDM signal group in an optical network including the OADM, the optical signal may not be transmitted successfully. Such situation is caused by, for example, deterioration of optical characteristics due to the transmission distance dependence, the dispersion characteristic of an optical fiber used to transmit the WDM signals, the erroneous setting of a wavelength route in the optical network, or the erroneous connection of an optical fiber.
According to an OADM conforming to Optical Transport Network (OTN), for example, the erroneous connection of an optical fiber is detected by referring to Source Access Point Identifier (SAPI) or Destination Access Point Identifier (DAPI) of an optical signal, which is included in Trail Trace Identifier (TTI) information provided in a frame.
Japanese Laid-open Patent Publication No. 2001-358657, Japanese Laid-open Patent Publication No. 2002-44035, etc. are disclosed as the related art.